# 需求(变量：单价，数量，总价)
# - 包子的价格是 **1.5 元/个**
# - 买了 **10 个** 包子
# - 今天老板高兴，总价打 9 折
# - 请重新计算购买金额
price = 1.5
number = 10
money = price * number  # 打折前
print("打折前",money)

# money = money * 0.9 # money = 15 * 0.9
money *= 0.9  # money = money * 0.9 的简写
print("打折后",money)